1. Field of the Invention
The present invention provides an improved method for the preparation of esters such as t-butyl acetate.
2. Description of the Prior Art
It is known to produce esters by the reaction of an olefin such as isobutylene with a lower carboxylic acid over a sulfonate group-containing cation exchange resin. See U.S. Pat. No. 3,678,099 and the references disclosed therein including U.S. Pat. Nos. 2,678,332, 3,031,495, 3,172,905 and 3,173,943.
A problem which is encountered in such prior procedures has been the tendency for polymerization of the olefin to occur during the esterification which results both in significant yield losses and in the formation of products such as olefin dimer which are difficult to separate from the product ester. For example, isobutylene dimer forms an azeotrope with t-butyl acetate thus making separation exceedingly difficult.
In accordance with the invention of said copending application, the production of olefin oligomers during reaction between olefin and lower carboxylic acid is reduced by carrying out the reaction in the presence of a selectivity enhancing modifier such as t-butyl alcohol. However, the addition of the selectivity enhancing modifier to the reaction system involves an added expense and possibly results in purification problems where the modifier contains impurities.
U.S. Pat. No. 4,011,272 relates to a method for the production of tertiary butyl alcohol by reaction of isobutylene with water in the presence of a sulfonic acid resin and an organic acid such as acetic acid. Water is used in at least equimolar amount relative to the isobutylene and tertiary butyl alcohol is the primary product. The patent teaches that the minor amounts of tertiary butyl acetate which are formed can readily be hydrolyzed to form additional tertiary butyl alcohol.